// Define pins for the IR sensors
#define IR_SENSOR_RIGHT 11 // Right IR sensor connected to pin 11
#define IR_SENSOR_LEFT 12  // Left IR sensor connected to pin 12

// Define the motor speed
#define MOTOR_SPEED 180 // Motor speed (PWM value between 0-255)

// Define pins for the right motor
const int enableRightMotor = 6; // PWM pin to control the speed of the right motor
const int rightMotorPin1 = 7;   // Pin to control the direction of the right motor (forward)
const int rightMotorPin2 = 8;   // Pin to control the direction of the right motor (backward)

// Define pins for the left motor
const int enableLeftMotor = 5;  // PWM pin to control the speed of the left motor
const int leftMotorPin1 = 9;    // Pin to control the direction of the left motor (forward)
const int leftMotorPin2 = 10;   // Pin to control the direction of the left motor (backward)

// Function prototypes for modular code
void setupMotors();         // Sets up the motor control pins
void setPWMFrequency();     // Adjusts the PWM frequency for smoother motor control
void controlMotors(int leftSpeed, int rightSpeed); // Controls motor speed and direction
int readLineSensors();      // Reads the IR sensors and returns a combined binary value

void setup()
{
  // Initialize motor pins
  setupMotors();

  // Adjust the PWM frequency for smoother motor control
  setPWMFrequency();

  // Initialize sensor pins as inputs
  pinMode(IR_SENSOR_RIGHT, INPUT);
  pinMode(IR_SENSOR_LEFT, INPUT);

  // Stop motors initially to ensure the robot does not move
  controlMotors(0, 0);
}

void loop()
{
  // Read the sensor values and determine the state of the robot
  int sensorState = readLineSensors();

  // Perform actions based on the sensor state using a switch-case statement
  switch (sensorState)
  {
    case 0b00: // No line detected by either sensor
      controlMotors(MOTOR_SPEED, MOTOR_SPEED); // Move straight
      break;

    case 0b01: // Line detected by the left sensor only
      controlMotors(MOTOR_SPEED, -MOTOR_SPEED); // Turn left
      break;

    case 0b10: // Line detected by the right sensor only
      controlMotors(-MOTOR_SPEED, MOTOR_SPEED); // Turn right
      break;

    case 0b11: // Line detected by both sensors
      controlMotors(0, 0); // Stop the robot
      break;

    default: // Fallback case to stop the robot for safety
      controlMotors(0, 0);
  }
}

// Function to initialize motor pins
void setupMotors()
{
  // Set motor control pins as outputs
  pinMode(enableRightMotor, OUTPUT);
  pinMode(rightMotorPin1, OUTPUT);
  pinMode(rightMotorPin2, OUTPUT);

  pinMode(enableLeftMotor, OUTPUT);
  pinMode(leftMotorPin1, OUTPUT);
  pinMode(leftMotorPin2, OUTPUT);
}

// Function to adjust PWM frequency for smoother motor control
void setPWMFrequency()
{
  // Set PWM frequency for pins 5 and 6 (Timer0)
  // Timer0 default frequency is ~490 Hz; this changes it to ~7812.5 Hz
  TCCR0B = TCCR0B & 0b11111000 | 0b00000010;
}

// Function to control motor speed and direction
void controlMotors(int rightSpeed, int leftSpeed)
{
  // Control the right motor direction
  digitalWrite(rightMotorPin1, rightSpeed > 0); // Forward if speed > 0
  digitalWrite(rightMotorPin2, rightSpeed < 0); // Backward if speed < 0

  // Control the left motor direction
  digitalWrite(leftMotorPin1, leftSpeed > 0); // Forward if speed > 0
  digitalWrite(leftMotorPin2, leftSpeed < 0); // Backward if speed < 0

  // Control the motor speeds using PWM
  analogWrite(enableRightMotor, abs(rightSpeed)); // Set speed for the right motor
  analogWrite(enableLeftMotor, abs(leftSpeed));   // Set speed for the left motor
}

// Function to read IR sensors and return a combined binary value
int readLineSensors()
{
  // Read the state of the right and left IR sensors
  int rightSensor = digitalRead(IR_SENSOR_RIGHT); // 0 = no line, 1 = line detected
  int leftSensor = digitalRead(IR_SENSOR_LEFT);   // 0 = no line, 1 = line detected

  // Combine the two sensor readings into a single binary number
  // Example: if rightSensor = 1 and leftSensor = 0, the result will be 0b10 (decimal 2)
  return (rightSensor << 1) | leftSensor;
}